Doing Too Much Too SoonBetween the steep hills, wind factor, uneven or slippery terrain, and not having a belt propelling you forward, running outside is harder than running on a treadmill. And since it's more taxing on your muscles, you are more prone to shin splints and other pains. Start off with shorter distances on flat roads or trails, and as your endurance improves, gradually increase your mileage and hill work. If you experience shin pain, take a few minutes to walk and stretch out your lower legs. Don't run through the pain because it may cause further injury, preventing you from running at all. When you're not running, strengthen your shins with this exercise.

Trying to Maintain a Constant PaceThe treadmill belt keeps a consistent pace for you, so it's easy to get into a rhythm. Outside is a whole new ballgame since you're in charge of maintaining your speed. Aside from using your own muscles to propel each step, the steeper inclines, road obstacles, and uneven terrain make it harder to run fast. Don't feel compelled to push yourself to run at the same pace you did on the treadmill you may end up falling or pulling a muscle. Run at a moderate and comfortable pace that allows you to run safely, and gradually increase your speed over several weeks. Check out these tips on how to become a faster runner.

Running on PavementAlthough easily accessible, pavement is a hard, unforgiving surface. Abruptly switching from a soft treadmill belt to a stiff road can be such a shock to the muscles and joints; some may find it hard to run half a mile without stopping in pain. Ease into running on the pavement by starting on the grassy areas between the sidewalk and the road, or better yet, stick to dirt roads or woodsy trails. Here are even more trail-running tips for the beginner.

Wearing the Wrong ShoesA regular running sneaker was perfect for the flat, predictable surface of a treadmill, but once you head outdoors, make sure your sneaker's tread can handle the gravel, dirt roads, and slick trails. You want a sneaker that supports your feet and offers a grippy sole so you feel confident moving over uneven surfaces.

Getting LostIt's easy to hit the ground running, but if you're not paying attention, you may end up in an unfamiliar neighborhood or woodsy trail, with no clue as to how to get home. The adrenaline that builds from a panicked feeling of being lost can often make you run faster without paying attention to where your feet step, increasing the likelihood of tripping. Prevent getting lost by planning new routes before you head out the door. Always bring your phone along and try one of the many iPhone running apps that use a GPS to keep track of your location (I use the Nike+ GPS app). Taking a running buddy is also a smart idea, and get in the habit of telling someone where you're going before you head out, just in case you get hurt or lost.